# Prosiectau Ffiseg ar gyfer myfyrwyr bl.3 a bl.4

### Wakeing up to wind power

#### (supervisor: Rudi Winter)

Nature of project: theory, software

Available to students on full-time physics degree schemes or joint students.

#### Project description and methodology

A wind turbine extracts momentum from the wind and uses it to drive a generator. The wind downstream of the turbine will obviously be a little less intense as we have taken energy away in the process. However, it will also be more turbulent because the rotor surface area exposed to the wind is changing all the time. This is where a wind turbine produces entropy in line with the Second Law.

If the wind turbine is part of a larger power station, then other turbines sited downstream will be affected by this reduction in energy and increase in turbulence of the wind. The latter is known as the wake effect of a turbine. It needs to be considered, along with the direction of the prevailing wind, when designing an array of turbines, because it can drastically reduce the efficiency of the downstream turbines in the array.

Fluid dynamics provides a range of modelling approaches to address wake effects in turbine arrays. In this project, we will investigate the equations involved. Software will be developed to simulate the reduction of efficiency under different siting scenarios, wind speeds and directions. The results will be validated against published anemometry data from marine wind turbine arrays.

A successful project will develop beyond the above in one/some of the following directions:
(1) Visualisation of the results: Draw maps showing the wind energy and turbulence calculated downstream of turbines or turbine arrays based on the simulations.

(2) Experiment with irregular arrays: Can the overall efficiency be increased if the turbines are sited on patterns other than a regular grid? How does the answer to this question depend on the uniformity (or otherwise) of the prevailing wind direction?

(3) A recent draft paper suggests that alternating the sense of rotation of adjacent turbines may improve array efficiency by reducing turbulence. Try to work this into your model.

When considering where to take your project, please bear in mind the time available. It is preferable to do fewer things well than to try many and not get conclusive results on any of them. However, sometimes it is useful to have a couple of strands of investigation in parallel to work on in case delays occur.

Additional scope or challenge if taken as a Year-4 project: A Y4 student could look into the thermodynamic aspect of entropy production. How do we need to adapt the concept of thermodynamic efficiency if the process we're studying isn't a heat engine?

Please speak to Rudi Winter (ruw) if you consider doing this project.

Initial literature for students:

1. T Göçmen et al., Renewable Sustainable Energy Rev 60 (2016) 752
2. NG Nygaard et al., J Phys Conf Ser 524 (2014) 012162
3. MF Howland et al., Proc Natl Acad Sci USA 116 (2019) 14495
4. A Englberger et al., Should wind turbines rotate in the opposite direction?; Wind Energy Sci Discuss (2020) in review

#### Novelty, degree of difficulty and amount of assistance required

Simulations on the analytical Jensen model of wind turbulence effects should be relatively straightforward to implement. Working out the cumulative effect of several turbines in an array may be a lot more challenging. The student is free in their choice of programming language; help can be provided in python or C.

#### Project milestones and deliverables (including timescale)

milestoneto be completed by
Identification of base model and a selection of detailed aspects of turbine arrays to be modelled.end of November
Outline of pseudo-code for the turbine array model softwareChristmas
Core Jensen model coded, tested and validated.end of February
Detailed aspects/variations of the model coded, tested and validated.Easter